NASA has revealed the science behind how astronauts can enjoy a coffee in low-gravity in space with a special "zero-G" coffee cup.

The problem for caffeine-seeking space travellers is that in low-gravity environments like a space station fluids tend to get "sticky", according to NASA.

"Surface tension and capillary effects, which are overwhelmed by gravity on Earth, rule the day in space," the US space authority said.

"As a result, coffee tends to cling to the walls of the cup."

However, the zero-G coffee cup solved these problems by "going with the flow", putting the strange behavior of fluid in microgravity to work.

An astronaut enjoys the geometry of the special zero-G coffee cup (Image: NASA)

The specially shaped cup is required because liquids become sticky in low gravity (Image: NASA)

In an interview with NASA Space Life and Physical Research and Applications Division director Marshall Porterfield, Dr Mark Weislogel from Portland State University revealed the cup was specially designed to take advantage of the forces in space and allow the coffee to be consumed.

"The coffee cup utilises all we have learned about capillary forces in space," he said.

"With that, we can make a cup large enough to still exploit capillary forces so that when the astronaut brings it to his face, there is a gradient in the driving force from surface tension to drive the liquid right into the mouth of the astronaut."

The angles of the cup allow the astronaut to drink the coffee at the desired speed without spilling any (Image: NASA)

This basic science theory can also be used to help create cooling or refrigeration systems in space, Dr Weislogel said.

He added: "In a way, we have designed a cup so that the bottom of the cup is actually the lip of the cup.

"When an astronaut makes that connection, that serves as the bottom and it will drain into the mouth at the rate he or she takes it in."